Neung K, 25, the manager of a small business in Bangkok, has already lost his wife and daughter to Aids. Two years ago, he began to feel ill himself. He was told he had cryptococcal meningitis, an infection that often kills people in Thailand whose immune system is compromised by the HIV virus. He was given a prescription for fluconazole, an antibiotic that is handed out without a murmur under the NHS in the UK.

But Neung could not pay the 15,000 bahts (US$450) a month the medicine cost out of his monthly income of 12,000 bahts (US$340). His illness cost him his job and he used up his savings paying for occasional treatment that gave him a little respite. He was lucky - Médècins Sans Frontières (MSF) stepped in to help - but there are many Thais in his predicament. Between 1984 and 1998, almost 1m out of 61m Thais were HIV positive and 500,000 cases are expected next year.

Medicines are a trade issue and thanks to health action groups like MSF, the World Trade Organisation in Seattle will be under pressure to strengthen its provisions to help some developing countries to bypass patent law in the interests of saving lives.

Medicine patent law was a sensitive subject in the last round of trade negotiations. The compromise was a loophole in the intellectual property agreement, Trips. It is called article 31 and authorises countries to make their own generic, cheap version of a medicine - with a payment to the pharmaceutical company holding the patent - in an emergency. In the jargon, this is "compulsory licensing". But attempts by countries like Thailand to use this provision have brought them into conflict with international pharmaceutical corporations.

The concern is that WTO rules are bypassed when it suits big commercial interests.

The pharmaceuticals see compulsory licensing as a threat to their profits. They have to recoup the billions of dollars they have spent within the life of their patent -Trips gives them 20 years.

Thailand used to allow its people to manufacture generic versions of drugs. It brought the cost of the Aids drug zidovudine, which can prevent mothers passing the HIV virus to their babies during labour, down from US$324 in 1992 to US$87 in 1995. In the second half of 1998, two companies produced fluconazole, which went on the market at a mere 4,000 bahts, a third of the price Neung used to pay.

But the Thai government has come under great pressure from the US government, driven by the powerful pharmaceutical industry lobby. The American government strongarmed the Thais into signing an undertaking not to allow compulsory licensing (although it is legal under Trips) by imposing import duties on wood, jewellery, micro-processors and other Thai goods. It is a striking example of how the US bypassed WTO agreements to protect its drug companies.

But the pharmaceutical industry is no longer having it all its own way. The catalyst has been Aids. The issue of a developing country's right to try to save lives by producing cheap medicines came home to the USA when Aids activists found out what had been going on in South Africa.

Jamie Love, who runs the US-based consumer project on technology which has led the campaign for access to essential medicines with MSF, brought to light the pressure the US government was putting on South Africa to stop "parallel importing" - buying drugs from countries where they are on sale more cheaply.

The issue suddenly became hot political news when members of Act Up, the American Aids pressure group, began targetting deputy president Al Gore this year. Gore had taken a big part, as joint chairman of the US/South Africa Binational Commission, pushing the interests of the drug companies and pressurising the South African government to prohibit parallel imports. The USA was not alone. In March 1998, Sir Leon Brittan wrote as a European commissioner to South Africa warning that legislation to allow parallel imports "would negatively affect the interests of the European pharmaceutical industry".

By June 25, Gore was supporting "South Africa's efforts to enhance health care for its people, including efforts to engage in compulsory licensing and parallel importing of pharmaceuticals".

At the same time, a battle has been going on to get the World Health Organisation (WHO) involved. After early resistance, it was finally agreed at the organisation's annual meeting in May that WHO should look at the impact of trade regulation on health and help countries address health needs while complying with the rules.

As Seattle looms, there is disappointment among activists because it seems that WHO is not going to raise the issue of access to medicines after all.

The pressure is now on the EU. MSF is campaigning for Europe to support access to essential medicines for the poorest. It is pointing out the hypocrisy of any other position.